Fixes a freshness issue with induction (see comment in #12944).

The names computed in consume_pattern were lost when calling
intros_pattern_core. Moreover, the computation of names to avoid was
done several time. We compute it once for all.

1 files changed, 1 insertions, 4 deletions

diff --git a/tactics/tactics.ml b/tactics/tactics.ml
index eb7b7e363f..00bd56d8ba 100644
--- a/tactics/tactics.ml
+++ b/tactics/tactics.ml
@@ -3248,13 +3248,10 @@ let rec consume_pattern avoid na isdep gl = let open CAst in function
   | {loc;v=IntroForthcoming true}::names when not isdep ->
       consume_pattern avoid na isdep gl names
   | {loc;v=IntroForthcoming _}::names as fullpat ->
-      let avoid = Id.Set.union avoid (explicit_intro_names names) in
       (CAst.make ?loc @@ intropattern_of_name gl avoid na, fullpat)
   | {loc;v=IntroNaming IntroAnonymous}::names ->
-      let avoid = Id.Set.union avoid (explicit_intro_names names) in
       (CAst.make ?loc @@ intropattern_of_name gl avoid na, names)
   | {loc;v=IntroNaming (IntroFresh id')}::names ->
-      let avoid = Id.Set.union avoid (explicit_intro_names names) in
       (CAst.make ?loc @@ IntroNaming (IntroIdentifier (new_fresh_id avoid id' gl)), names)
   | pat::names -> (pat,names)
 
@@ -3312,7 +3309,7 @@ let get_recarg_dest (recargdests,tophyp) =
 *)
 
 let induct_discharge with_evars dests avoid' tac (avoid,ra) names =
-  let avoid = Id.Set.union avoid avoid' in
+  let avoid = Id.Set.union avoid' (Id.Set.union avoid (explicit_intro_names names)) in
   let rec peel_tac ra dests names thin =
     match ra with
     | (RecArg,_,deprec,recvarname) ::